As the article states, there is no definition of a "resting" observer within Special Relativity. However, we do have a definition of a moving observer. In fact, there is a moving observer who always has the same velocity:Photons. The velocity of light is a constant and no matter into which moving coordinate-system you transform the movement of the photon, it always moves at the speed of light.

Why is this interesting? Because it allows us to measure how fast the Universally Accelerating Flat Earth is right now, measured as a percentage of the speed of light, which is a hard, well-known number.

If Flat Earth experiences a constant acceleration of 9.81 m/s², after 1 year = 31,557,600 seconds it has a velocity of approximately 3*10^8 m/s. That's light-speed. Now, of course we are not moving at light-speed, but this simple estimate makes it reasonable to assume that Flat Earth has been moving at a velocity close to the speed of light since a few years after its creation.

What happens if you throw a ball horizontally at a constant velocity? It will fall down and its trajectory is a parable. The same would happen to a photon in a Universally Accelerating Flat Earth.

The photon is moving horizontally at a constant velocity, while the frame of reference is moving upwards with an acceleration. That means, to an observer within the frame of reference the photon is moving downwards.

The experiment is simple:1. You hold a laserpointer horizontally and activate it. 2. By holding the sheet of paper at various distances to the laserpointer, you can make the trajectory of the photons visible.3. As you know the speed of light, you can calculate the present velocity of Universally Accelerated Flat Earth based on how the beam of light drops down to Flat Earth.

The formula for evaluation is simple: 1. The photon reaches a paper held at a distance of 1 meter after a time t = 1 meter / c2. We assume that 1 meter is an such an insignificant length for an object moving at the speed of light, that we can estimate for Flat Earth to have a constant velocity during that short interval of time.3. We measure the drop-off d of the beam of light, compared to the horizontal axis defined by our laser-pointer.4. We calculate d/t, and now we know how fast Flat Earth has been on average during our experiment.

For example:If the beam of light has a drop-off of 0,1 m over a distance of 1 m, then Flat Earth had an average velocity of 10% of speed of light during the measurement.

Your claims about "knowing a thing or two" are irrelevant. You're assuming that the light would not be subjected to the initial velocity of its source. That, of course, would directly contradict your claims about the Doppler Effect. You've already debunked yourself.

Your claims about "knowing a thing or two" are irrelevant. You're assuming that the light would not be subjected to the initial velocity of its source. That, of course, would directly contradict your claims about the Doppler Effect. You've already debunked yourself.

Are you trolling?

The velocity of light is a constant that doesn't change if you transform from one moving coordinate-system to another moving coordinate-system. That's Special Relativity in a nutshell. Seriously, grab a physics-book.

The Doppler-Effect does not change the velocity of the wave. It changes how I observe the frequency of the wave. Double-seriously, grab a physics-book.

If you don't understand what I wrote, say so and I will explain it in more detail.

I see you don't have much of use to say. Unsurprising. So far, your proposed substantiation is "hehe I know physics" and "grab a book". You will find that the standards here are a bit higher than that.

I'm with Pete here. Within in a frame of reference, regardless of external speed, even if it's a significant percentage of the speed of light, light appears to travel at the speed of light inside that frame of reference.

I see you don't have much of use to say. Unsurprising. So far, your proposed substantiation is "hehe I know physics" and "grab a book". You will find that the standards here are a bit higher than that.

I'm with Pete here. Within in a frame of reference, regardless of external speed, even if it's a significant percentage of the speed of light, light appears to travel at the speed of light inside that frame of reference.

Michael from VSauce explains this in his usual fun manner.

That was my claim. Pete thinks that a moving source changes the speed of light.

I do not. If you're not going to engage your debate partners honestly, please take it to Angry Ranting.

Speed and velocity are not the same? What definitions are you using?

My claim is that the accelerating frame of reference moves upward while the photon moves sideways because it does not move upwards because the speed of light is a constant and you can't vector-add the velocity of the moving source to the velocity of the photon. Accordingly, the photon does not move upwards while the system within we measure the location of the photon does move upwards, thereby creating a trajectory within the system that looks as if the photon is moving downwards.

My claim is that the accelerating frame of reference moves upward while the photon moves sideways because it does not move upwards

This is in direct contradiction of Special Relativity. Within our frame of reference, the photon doesn't move downwards, because the speed of light is constant. Your error is mixing up different frames of reference, which is unacceptable in the context of SR. Your claim would result in an observer locally perceiving light as moving faster than c.

My claim is that the accelerating frame of reference moves upward while the photon moves sideways because it does not move upwards because the speed of light is a constant and you can't vector-add the velocity of the moving source to the velocity of the photon. Accordingly, the photon does not move upwards while the system within we measure the location of the photon does move upwards, thereby creating a trajectory within the system that looks as if the photon is moving downwards.

I understand where you are coming from, but the sideways movement of the photon is included in the moving frame of reference. You are correct you cannot vector-add the velocity of the moving source to the velocity of the photon, but that is from a point of view external to the frame of reference. Within the frame of reference there is no problem adding the vectors.

Note: I an not a FE proponent. If I were, I would not be a UA proponent, too many problem. However, the acceleration part of UA is sound.

My claim is that the accelerating frame of reference moves upward while the photon moves sideways because it does not move upwards

This is in direct contradiction of Special Relativity. Within our frame of reference, the photon doesn't move downwards, because the speed of light is constant. Your error is mixing up different frames of reference, which is unacceptable in the context of SR. Your claim would result in an observer locally perceiving light as moving faster than c.

While this also invalidates my experiment with the Doppler-Effect on light-bulbs, I don't think it would affect a Doppler-Effect between a Universally Accelerating Flat-Earth and starlight. Would it? Because the source of the photon and Earth are moving independently. There would be more blueshift above in the nightsky than near the horizon of the nightsky.

EDIT: To clarify: There would be more blue-shifted stellar objects in the upwards direction in the nightsky than in a sideways direction in the nightsky.

I have a question regarding the speed of light. From a flat Earth perspective, where the entire universe revolves around the Earth once every 24 hours, how can it be that the furthest galaxies are rotating around the Earth? Wouldn't they need to be moving many tens of thousands times the speed of light to rotate around the Earth once every 24 Earth hours?

While this also invalidates my experiment with the Doppler-Effect on light-bulbs, I don't think it would affect a Doppler-Effect between a Universally Accelerating Flat-Earth and starlight. Would it? Because the source of the photon and Earth are moving independently.

Doppler effect only occurs when light source is moving relative to the observer. But in the flat earth model the Universally Accelerating does not move the stars towards or from the earth.

There would be more blueshift above in the nightsky than near the horizon of the nightsky.

EDIT: To clarify: There would be more blue-shifted stellar objects in the upwards direction in the nightsky than in a sideways direction in the nightsky.

This has nothing to do with any blue-shift as a result of motion. What you are referring to here is the scattering effect of the atmosphere. Blue light is more scattered by the atmosphere than the wavelength of red light. That's why the sky is blue and the light of the sun turns to red when it has to travel a longer distance trough the atmosphere to reach our eye.

He who believes windmills are his enemies, will take the gentle turning of their blades an act of aggression, and mistake their soft murmur for angry ranting.

While this also invalidates my experiment with the Doppler-Effect on light-bulbs, I don't think it would affect a Doppler-Effect between a Universally Accelerating Flat-Earth and starlight. Would it? Because the source of the photon and Earth are moving independently.

Doppler effect only occurs when light source is moving relative to the observer. But in the flat earth model the Universally Accelerating does not move the stars towards or from the earth.

There would be more blueshift above in the nightsky than near the horizon of the nightsky.

EDIT: To clarify: There would be more blue-shifted stellar objects in the upwards direction in the nightsky than in a sideways direction in the nightsky.

This has nothing to do with any blue-shift as a result of motion. What you are referring to here is the scattering effect of the atmosphere. Blue light is more scattered by the atmosphere than the wavelength of red light. That's why the sky is blue and the light of the sun turns to red when it has to travel a longer distance trough the atmosphere to reach our eye.

1. That depends on whether we use the model where the stars are out in the universe or whether we use a model where they are glued onto Earth's dome. If they are not glued to Earth, then their light is blueshifted due to Earth's movement.

2. I don't mean Rayleigh-scattering. I mean that that there is an angle between the vector-movement of Earth and the direction from which the light of a star reaches us. That means that the relative velocity between Earth and the star along the Earth-star axis depends on where the star is relative to Earth's movement. And if the relative velocity depends on the angle, then there is a different blueshift between angles.

Starlight in front of Earth is blueshifted, starlight behind Earth is redshifted. And the horizon is the angle where there is neither blueshift nor redshift.

My claim is that the accelerating frame of reference moves upward while the photon moves sideways because it does not move upwards

This is in direct contradiction of Special Relativity. Within our frame of reference, the photon doesn't move downwards, because the speed of light is constant. Your error is mixing up different frames of reference, which is unacceptable in the context of SR. Your claim would result in an observer locally perceiving light as moving faster than c.

You are partially correct, but otherwise entirely wrong. I will demonstrate.

The thing that differentiates vectors from scalars is direction. But that is contingent upon direction parallel to motion. Indeed, motion perpendicular to acceleration has no SR effect. It is the component parallel to the direction of motion which experiences Lorentz contraction. For this exact reason, your statements are completely backwards, but would apply to motion perpendicular.

So you see Peter, the photon would move down, precisely because it must accord with SR. This is one of Einstein's famous thought experiments.

The fact.that it's an old equation without good.demonstration of the underlying mechamism behind it makes.it more invalid, not more valid!